1. Field of the Invention:
The invention relates to a method for cancelling a payment transaction with an electronic payment means, such as a so-called smart card or chip card. The invention further relates to a payment means for application of the method, as well as to a payment system in which the method is applied.
2. Discussion of Background:
Electronic payment means, such as debit cards provided with an integrated circuit (chip cards), are known in practice. Payment systems which make use of electronic payment means, can be subdivided into so-called on-line systems, in which a payment station (such as an electronic cash register) exchanges data with a payment institution (such as a bank) during a transaction, and off-line systems, where such a data exchange does not need to be carried out during each transaction. In off-line systems, the insusceptibility to fraud is entirely dependent upon the protections which are built into the payment means and the payment station, since no verification is carried out at the payment institution.
There exists a need to be able to cancel payment transactions. For payment transactions which are effected with cash it is usually no problem to refund excess money paid or money paid wrongly, for example if an error is made in a payment transaction or if a customer on second thoughts decides not to purchase a certain article. In electronic payment systems the problem arises that restitution of money, for example by incrementing a card balance, is in general not possible in order to rule out misuse. Particularly in the off-line systems mentioned this is a problem, since no verification of the payment means or of the transaction is possible at the payment institution concerned. The state of the art does not supply an explicit solution for this problem.
European Patent Application EP 0,637,004 discloses a method for devaluing debit cards in a protected manner, in which the exchange of data between debit card and payment station takes place, possibly during a card verification routine. There is no question of cancelling the debited amount, however.
European Patent Application EP 0,630,027 discloses a method for writing a memory (EEPROM) on an electronic debit card (smart card) in a protected way, with the object of preventing the accidental erasure of data. Cancelling a completed transaction is not described in said document.
European Patent Application EP 0,627,714 discloses a device for effecting transactions with a card. With the aid of this prior art device, transactions can be cancelled if certain cancel data are available. However, this publication does not disclose what these cancel data consist of and in which way the cancellation is carried out. Neither does a protection protocol appear to be used.
The prior art, therefore, does not offer a method and a device for cancelling, in a protected manner, a transaction with an electronic debit card in an off-line system.